The broadest distinction between sources of organic waste within aquatic ecosystems can be by grouping waste as either from plant or animal matter. Aquatic ecosystems do host plant life such as algae and macrophytes. Often, during periods of excess nutrients into the ecosystem, called eutrophication, algal and macrophyte growth will experience an explosion. Once the nutrients are depleted, the algae and macrophytes will begin to die off, introducing organic waste to the system. Animal-based waste within an aquatic ecosystem can result from defecation by fish and water birds, as well as the death of organsims.